Due to developments in genetic engineering in recent years, in the medical field, diagnosis and prevention of diseases by genes has come to be possible. Diagnosis by using genetic engineering is called gene diagnosis. In gene diagnosis, by detecting defect or change in a gene of a human, which may be source of a disease, diagnosis or measurement can be carried out before the onset of a disease or at the initial stage thereof. Further, by detecting a gene of a contracted virus or pathogenic bacteria, an accurate diagnosis is possible.
A general gene detecting method conventionally used is as follows.
First, a gene is extracted from a sample. If necessary, the gene is cut by appropriate restriction endonuclease, and thereafter, electrophoresis and Southern plotting are carried out. Next, a nuclease probe having a base sequence complementary to the target gene which is the object of detection is hybridized with the plotted gene. Note that the nuclease probe is usually labeled by a fluorescent dye. Then, the fluorescent dye is excited by laser light. Accordingly, the hybridized nuclease probe is detected, and the existence of the target gene is verified.
However, in this detecting method using a fluorescent dye, it takes at least a few days until detection of a gene. Further, the nuclease probe must be labeled by a high-priced fluorescent dye. In addition, a laser generating device for exciting the fluorescent dye is needed, and the device becomes large.
In order to solve the above-described problems of the detecting method using a fluorescent dye, a gene detecting method using an electrochemical method has been conceived of. The detecting method using an electrochemical method is disclosed in Japanese Patent No. 2573443 conceived of by the present inventors, and the contents thereof are incorporated herein by reference. In accordance with this electrochemical method, detecting an electrochemical signal from an electrode having a probe immobilized thereto allows existence of the target gene to be verified.
However, in gene detection using an electro-chemical method, background current arises at the time of current detection. Accordingly, current caused by derivation with the probe and the background current are included in the current value detected from the electrode. Therefore, from the results of detection, it has been difficult to extract only the current derived from the probe.